This invention relates to an apparatus and a method for roll shifting a chockless work roll of a cluster mill.
A conventional work roll shift apparatus of a cluster mill will be described based on FIGS. 11 and 12. FIG. 11 is a schematic configuration drawing of a cluster mill with 20 rolls which is called a Sendzimir mill, and FIG. 12 is a view taken on line XIIxe2x80x94XII in FIG. 11.
The illustrated cluster mill is composed of upper and lower chockless work rolls 50 as a pair, two chocked upper first intermediate rolls 51 and two chocked lower first intermediate rolls 51, three chocked upper second intermediate rolls 52 and three chocked lower second intermediate rolls 52, and four chocked upper backup rolls 53 and four chocked lower backup rolls 53. The numeral 60 denotes a material to be rolled which is passed between the upper and lower work rolls 50.
The cluster mill of the illustrated type is used to roll a stainless steel plate, a nickel-chromium steel plate, etc. It is designed such that the small-diameter, undriven, movable work rolls 50 are held so as to be constrained between the two upper first intermediate rolls 51 and the two lower first intermediate rolls 51, and the movement of the work roll 50 in the axial direction is restrained by a thrust bearing provided at a position opposed to the end of the work roll 50.
FIG. 12 shows an end portion of the work roll 50 of the cluster mill. In the drawing, 50a denotes an end flange of the work roll 50, and 51a denotes a chock of the first intermediate roll 51. The work roll 50 is provided so as to have a length with which the end flange 50a is located deep near the inside of the chock 51a of the first intermediate roll 51. At this position, a revolving thrust bearing 54 is provided which spreads over the two (upper and lower) end flanges 50a in such a manner as to be opposed to the outer surfaces of the end flanges 50a with a slight clearance. Thus, the axial movement of the work rolls 50 is suppressed by the thrust bearing 54.
In the illustrated cluster mill, in order to facilitate the withdrawal and replacement of the work roll 50 suffering from marked wear and tear, the thrust bearing 54 is supported on the ends of rods of a pair of cylinders 55, whereby the work rolls 50 are moved together with the thrust bearing 54 over a certain distance as shown by chain lines in the drawing.
With a chocked work roll mill having a small number of rolls, for example, for hot rolling of a steel material, a roll shifting configuration for shifting upper and lower chocked work rolls in the axial direction has found use as a method for control of a plate surface shape during rolling.
With the cluster mill shown in FIGS. 11 and 12, on the other hand, the work roll 50 has a chockless structure and is undriven. Thus, roll shift by a mechanical structure as in the hot rolling mill is not applicable, and a work roll shift apparatus for cluster mills has not been under development.
The present invention has been accomplished in light of the above-described circumstances, and its object is to provide a work roll shift apparatus and a work roll shift method which can be put to practical use in the cluster mill.
A work roll shift apparatus for a cluster mill according to the present invention is a work roll shift apparatus adapted to shift a chockless work roll of the cluster mill having the chockless work rolls, characterized by:
lever arms each supported at one end by a chock of rolls adjacent to the chockless work roll, and provided so as to be horizontally pivotable about a line perpendicular to an axis line of the work roll as a neutral point;
roll shifting cylinders each connected to the lever arm so as to pivot the lever arm;
thrust bearings each provided on the lever arm and opposed to an end of the work roll;
shift amount detecting means each provided in the chock of the rolls for detecting a shift amount of the thrust bearing; and
a control unit for driving the roll shifting cylinder so as to maintain a clearance between the work roll and the thrust bearings and obtain a target roll shift position based on a shift amount performance value of the thrust bearing obtained by the shift amount detecting means.
According to this feature, a chockless mill, such as a Sendzimir mill or other cluster mill, can be effectively used as the work roll shift mill. Moreover, shift control of the upper and lower work rolls takes place by different routes, so that the upper and lower shift positions can be set freely. For example, shift of the upper and lower work rolls in opposite directions in response to changes in the plate width, or shift of the upper and lower work rolls in the same direction following a zigzag motion of the plate can be freely set and performed.
The work roll shift apparatus for a cluster mill is also characterized in that the lever arm is composed of a frame structure having insert-through holes through which the rolls are inserted so as to be freely fitted with play; that the work roll is composed of a tapered roll; and that the work roll is composed of a tapered roll.
A work roll shift method for a cluster mill according to the present invention is a work roll shift method for a cluster mill, adapted to shift a chockless work roll in a required shift amount by possessing thrust bearings opposed to both ends of the chockless work roll so as to be capable of being relieved or pushed in by shifting cylinders, securing a constant clearance between the ends of the work roll and the thrust bearings, and blocking the shifting cylinder, characterized by:
multiple-dividing the required shift amount of the work roll to set short shift amounts as units;
performing a relief action for one of the thrust bearings and a push-in action for the other thrust bearing in each short shift amount, based on a shift amount performance value of the thrust bearing, so as to obtain a target roll shift position;
then blocking the shifting cylinder; and
repeating shift in each short shift amount and a blocking action for the shifting cylinder to shift the work roll in the required shift amount.
According to this feature, the effect that the chockless work roll of the cluster mill can be roll-shifted safely and highly precisely can be obtained.